--- a/mobile/android/base/java/org/mozilla/gecko/preferences/GeckoPreferences.java
+++ b/mobile/android/base/java/org/mozilla/gecko/preferences/GeckoPreferences.java
@@ -169,16 +169,17 @@ public class GeckoPreferences
     public static final String PREFS_READ_PARTNER_BOOKMARKS_PROVIDER = NON_PREF_PREFIX + "distribution.read_partner_bookmarks_provider";
     public static final String PREFS_CUSTOM_TABS = NON_PREF_PREFIX + "customtabs";
     public static final String PREFS_ACTIVITY_STREAM = NON_PREF_PREFIX + "activitystream";
     public static final String PREFS_CATEGORY_EXPERIMENTAL_FEATURES = NON_PREF_PREFIX + "category_experimental";
     public static final String PREFS_COMPACT_TABS = NON_PREF_PREFIX + "compact_tabs";
     public static final String PREFS_SHOW_QUIT_MENU = NON_PREF_PREFIX + "distribution.show_quit_menu";
     public static final String PREFS_SEARCH_SUGGESTIONS_ENABLED = "browser.search.suggest.enabled";
     public static final String PREFS_DEFAULT_BROWSER = NON_PREF_PREFIX + "default_browser.link";
+    public static final String PREFS_SYSTEM_FONT_SIZE = NON_PREF_PREFIX + "font.size.use_system_font_size";
 
     private static final String ACTION_STUMBLER_UPLOAD_PREF = "STUMBLER_PREF";
 
 
     // This isn't a Gecko pref, even if it looks like one.
     private static final String PREFS_BROWSER_LOCALE = "locale";
 
     public static final String PREFS_RESTORE_SESSION = NON_PREF_PREFIX + "restoreSession3";

--- a/mobile/android/base/locales/en-US/android_strings.dtd
+++ b/mobile/android/base/locales/en-US/android_strings.dtd
@@ -370,16 +370,21 @@ same character/combination is used to in
 representation of the language it is used in that will help show the text in the preview will change
 size. -->
 <!ENTITY pref_font_size_adjust_char "A">
 
 <!-- Localization note (pref_font_size_preview_text): This paragraph is used as an example to
     demonstrate the font size setting.  It is meant to be whimsical and fun. -->
 <!ENTITY pref_font_size_preview_text "The quick orange fox jumps over your expectations with more speed, more flexibility and more security. As a non-profit, we\'re free to innovate on your behalf without any pressure to compromise. That means a better experience for you and a brighter future for the Web.">
 
+<!-- Localization note (pref_use_system_font_size, pref_use_system_font_size_summary):
+     Font size here refers to the name of the corresponding Android system setting. -->
+<!ENTITY pref_use_system_font_size "Use system font size">
+<!ENTITY pref_use_system_font_size_summary "Scale web content according to the system font size">
+
 <!ENTITY pref_media_autoplay_enabled "Allow autoplay">
 <!ENTITY pref_media_autoplay_enabled_summary "Control if websites can autoplay videos and other media content">
 <!ENTITY pref_zoom_force_enabled "Always enable zoom">
 <!ENTITY pref_zoom_force_enabled_summary "Force override so you can zoom any page">
 <!ENTITY pref_voice_input "Voice input">
 <!ENTITY pref_voice_input_summary2 "Allow voice dictation in the URL bar">
 <!ENTITY pref_qrcode_enabled "QR code reader">
 <!ENTITY pref_qrcode_enabled_summary2 "Allow QR scanner in the URL bar">

--- a/mobile/android/base/resources/xml/preferences_accessibility.xml
+++ b/mobile/android/base/resources/xml/preferences_accessibility.xml
@@ -9,16 +9,20 @@
 
     <org.mozilla.gecko.preferences.FontSizePreference
                     android:key="font.size.inflation.minTwips"
                     android:title="@string/pref_text_size"
                     android:positiveButtonText="@string/pref_font_size_set"
                     android:negativeButtonText="@string/button_cancel"
                     android:persistent="false" />
 
+    <SwitchPreference android:key="android.not_a_preference.font.size.use_system_font_size"
+                      android:title="@string/pref_use_system_font_size"
+                      android:summary="@string/pref_use_system_font_size_summary" />
+
     <SwitchPreference android:key="browser.ui.zoom.force-user-scalable"
                       android:title="@string/pref_zoom_force_enabled"
                       android:summary="@string/pref_zoom_force_enabled_summary" />
 
     <SwitchPreference android:key="ui.zoomedview.enabled"
                       android:title="@string/pref_magnifying_glass_enabled"
                       android:summary="@string/pref_magnifying_glass_enabled_summary" />
 

--- a/mobile/android/base/strings.xml.in
+++ b/mobile/android/base/strings.xml.in
@@ -261,16 +261,18 @@
   <string name="pref_font_size_tiny">&pref_font_size_tiny;</string>
   <string name="pref_font_size_small">&pref_font_size_small;</string>
   <string name="pref_font_size_medium">&pref_font_size_medium;</string>
   <string name="pref_font_size_large">&pref_font_size_large;</string>
   <string name="pref_font_size_xlarge">&pref_font_size_xlarge;</string>
   <string name="pref_font_size_set">&pref_font_size_set;</string>
   <string name="pref_font_size_adjust_char">&pref_font_size_adjust_char;</string>
   <string name="pref_font_size_preview_text">&pref_font_size_preview_text;</string>
+  <string name="pref_use_system_font_size">&pref_use_system_font_size;</string>
+  <string name="pref_use_system_font_size_summary">&pref_use_system_font_size_summary;</string>
   <string name="pref_media_autoplay_enabled">&pref_media_autoplay_enabled;</string>
   <string name="pref_media_autoplay_enabled_summary">&pref_media_autoplay_enabled_summary;</string>
   <string name="pref_zoom_force_enabled">&pref_zoom_force_enabled;</string>
   <string name="pref_zoom_force_enabled_summary">&pref_zoom_force_enabled_summary;</string>
   <string name="pref_voice_input">&pref_voice_input;</string>
   <string name="pref_voice_input_summary">&pref_voice_input_summary2;</string>
   <string name="pref_qrcode_enabled">&pref_qrcode_enabled;</string>
   <string name="pref_qrcode_enabled_summary">&pref_qrcode_enabled_summary2;</string>